A wireless sensor network, WSN, is a group of devices with wireless communication infrastructure and sensors to monitor and record conditions at diverse locations. Sensors are typically autonomous devices with limited power supply.
Different networks have specific characteristics that could be utilized for novel services by a user equipment such as mobile phone. One example of a multimode user equipment can access both a mobile data network and a wireless sensor network. The user equipment may also act as a gateway for the wireless sensor network, combining mobility and large data transmission capability to the measurement data from the sensor network.
As the energy consumption is critical for the wireless sensor network elements, an access method for the multimode user equipment becomes an important factor. One conventional WSN access method for wireless sensor network elements is a MAC protocol (MAC, Medium Access Control). Conventional access methods cause unnecessary collisions between the multimode user equipment and the wireless sensor network, thus reducing the spectral efficiency and sensor network density. Conventional access methods are suitable for wireless sensor networks including mainly WSN elements. The sensor elements are traditionally in a fairly static location in relation to the network. The multimode user equipment on the other hand is characteristically mobile, therefore creating a need for a more effective accessing method.